1. Field of the Invention
This invention relates to a method of operating an internal combustion engine which enables improved purification or conversion of the exhaust gases thereof.
2. Brief Description of the Prior Art
It is known that nitrogen oxides and inflammable gases, such as carbon monoxide, hydrocarbons and the like, that is, harmful gases, are contained in the exhaust gases which are being exhausted from the internal combustion engines of motor vehicles. Accordingly, various attempts have been made to prevent such harmful gases from being discharged into the atmosphere.
Among the many improvements in this field which have heretofore been provided for avoiding the discharge of such harmful gases is one in which liquid fuel, such as gasoline or the like, is reformed into a reformed gas consisting essentially of hydrogen and carbon monoxide, with which a great amount of air is then mixed so as to provide a lean mixture gas, and then the mixture gas, thus prepared, is fed into an internal combustion engine for so-called "lean burning." This lean burning results in lowering of the combustion temperature within the engine, thereby enabling the quantity of nitrogen oxide to be lowered to a value as low as about 100 to 20 ppm. However, in this lean burning, a relatively great amount of unburned gases, such as unburned carbon monoxide and hydrocarbons and the like, which are residual in the aforesaid reformed gas, remains in the exhaust gases. For instance, about 0.2% of carbon monoxide and about 500 ppm. of hydrocarbons remains, which constitutes a disadvantage of such lean burning.